Show how many solutions are in the solution set for the equation 3x2=21

To solve the equation \(3x^2 = 21\), we first divide both sides by 3:

\[ x^2 = \frac{21}{3} \] \[ x^2 = 7 \]

Next, we take the square root of both sides:

\[ x = \pm\sqrt{7} \]

This gives us two solutions: \(x = \sqrt{7}\) and \(x = -\sqrt{7}\).

Therefore, there are two solutions in the solution set for the equation \(3x^2 = 21\).

The answer is: two.